Category Archives: Statistics

DNA: In Search of…Full and Half-Siblings

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This is the fifth article in our series of articles about searching for unknown close family members, specifically; parents, grandparents, or siblings. However, these same techniques can be applied by genealogists to identify ancestors further back in time as well.

Please note that if a family member has tested and you do NOT see their results, ask them to verify that they have chosen to allow matching and for other people to view them in their match list. That process varies at different vendors.

You can also ask if they can see you in their results.

All Parties Need to Test

Searching for unknown siblings isn’t exactly searching, because to find them, they, themselves, or their descendant(s) must have taken a DNA test at the same vendor where you tested or uploaded a DNA file.

You may know through any variety of methods that they exist, or might exist, but if they don’t take a DNA test, you can’t find them using DNA. This might sound obvious, but I see people commenting and not realizing that the other sibling(s) must test too – and they may not have.

My first questions when someone comments in this vein are:

  1. Whether or not they are positive their sibling actually tested, meaning actually sent the test in to the vendor, and it was received by the testing company. You’d be surprised how many tests are living in permanent residence on someone’s countertop until it gets pushed into the drawer and forgotten about.
  2. If the person has confirmed that their sibling has results posted. They may have returned their test, but the results aren’t ready yet or there was a problem.
  3. AND that both people have authorized matching and sharing of results. Don’t hesitate to reach out to your vendor’s customer care if you need help with this.

Sibling Scenarios

The most common sibling scenarios are when one of two things happens:

  • A known sibling tests, only to discover that they don’t match you in the full sibling range, or not at all, when you expected they would
  • You discover a surprise match in the full or half-sibling range

Let’s talk about these scenarios and how to determine:

  • If someone is a sibling
  • If they are a full or half-sibling
  • If a half-sibling, if they descend from your mother or father

As with everything else genetic, we’ll be gathering and analyzing different pieces of evidence along the way.

Full and Half-Siblings

Just to make sure we are all on the same page:

  • A full sibling is someone who shares both parents with you.
  • A half-sibling is someone who shares one parent with you, but not the other parent.
  • A step-sibling is someone who shares no biological parents with you. This situation occurs when your parent marries their parent, after you are both born, and their parent becomes your step-parent. You share neither of your biological parents with a step-sibling, so you share no DNA and will not show up on each other’s match lists.
  • A three-quarters sibling is someone with whom you share one parent, but two siblings are the other parent. For example, you share the same mother, but one brother fathered you, and your father’s brother fathered your sibling. Yes, this can get very messy and is almost impossible for a non-professional to sort through, if even then. (This is not a solicitation. I do not take private clients.) We will not be addressing this situation specifically.

Caution

With any search for unknown relatives, you have no way of knowing what you will find.

In one’s mind, there are happy reunions, but you may experience something entirely different. Humans are human. Their stories are not always happy or rosy. They may have made mistakes they regret. Or they may have no regrets about anything.

Your sibling may not know about you or the situation under which you, or they, were born. Some women were victims of assault and violence, which is both humiliating and embarrassing. I wrote about difficult situations, here.

Your sibling or close family member may not be receptive to either you, your message, or even your existence. Just be prepared, because the seeking journey may not be pain-free for you or others, and may not culminate with or include happy reunions.

On the other hand, it may.

Please step back and ponder a bit about the journey you are about to undertake and the possible people that may be affected, and how. This box, once opened, cannot be closed again. Be sure you are prepared.

On the other hand, sometimes that box lid pops off, and the information simply falls in your lap one day when you open your match list, and you find yourself sitting there, in shock, staring at a match, trying to figure out what it all means.

Congratulations, You Have a Sibling!

This might not be exactly what runs through your mind when you see that you have a very close match that you weren’t expecting.

The first two things I recommend when making this sort of discovery, after a few deep breaths, a walk, and a cup of tea, are:

  • Viewing what the vendor says
  • Using the DNAPainter Shared cM Relationship Chart

Let’s start with DNAPainter.

DNAPainter

DNAPainter provides a relationship chart, here, based on the values from the Shared cM Project.

You can either enter a cM amount or a percentage of shared DNA. I prefer the cM amount, but it doesn’t really matter.

I’ll enter 2241 cM from a known half-sibling match. To enter a percent, click on the green “enter %.”

As you can see, statistically speaking, this person is slightly more likely to be a half-sibling than they are to be a full sibling. In reality, they could be either.

Looking at the chart below, DNAPainter highlights the possible relationships from the perspective of “Self.”

The average of all the self-reported relationships is shown, on top, so 2613 for a full sibling. The range is shown below, so 1613-3488 for a full sibling.

In this case, there are several possibilities for two people who share 2241 cM of DNA.

I happen to know that these two people are half-siblings, but if I didn’t, it would be impossible to tell from this information alone.

The cM range for full siblings is 1613-3488, and the cM range for half-siblings is 1160-2436.

  • The lower part of the matching range, from 1160-1613 cM is only found in half-siblings.
  • The portion of the range from 1613-2436 cM can be either half or full siblings.
  • The upper part of the range, from 2436-3488 cM is only found in full siblings.

If your results fall into the center portion of the range, you’re going to need to utilize other tools. Fortunately, we have several.

If you’ve discovered something unexpected, you’ll want to verify using these tools, regardless. Use every tool available. Ranges are not foolproof, and the upper and lower 10% of the responses were removed as outliers. You can read more about the shared cM Project, here and here.

Furthermore, people may be reporting some half-sibling relationships as full sibling relationships, because they don’t expect to be half-siblings, so the ranges may be somewhat “off.”

Relationship Probability Calculator

Third-party matching database, GEDmatch, provides a Relationship Probability Calculator tool that is based on statistical probability methods without compiled user input. Both tools are free, and while I haven’t compared every value, both seem to be reasonably accurate, although they do vary somewhat, especially at the outer ends of the ranges.

When dealing with sibling matches, if you are in all four databases, GEDmatch is a secondary resource, but I will include GEDmatch when they have a unique tool as well as in the summary table. Some of your matches may be willing to upload to GEDmatch if the vendor where you match doesn’t provide everything you need and GEDmatch has a supplemental offering.

Next, let’s look at what the vendors say about sibling matches.

Vendors

Each of the major vendors reports sibling relationships in a slightly different way.

Sibling Matches at Ancestry

Ancestry reports sibling relationships as Sister or Brother, but they don’t say half or full.

If you click on the cM portion of the link, you’ll see additional detail, below

Ancestry tells you that the possible relationships are 100% “Sibling.” The only way to discern the difference between full and half is by what’s next.

If the ONLY relationship shown is Sibling at 100%, that can be interpreted to mean this person is a full sibling, and that a half-sibling or other relationship is NOT a possibility.

Ancestry never stipulates full or half.

The following relationship is a half-sibling at Ancestry.

Ancestry identifies that possible range of relationships as “Close Family to First Cousin” because of the overlaps we saw in the DNAPainter chart.

Clicking through shows that there is a range of possible relationships, and Ancestry is 100% sure the relationship is one of those.

DNAPainter agrees with Ancestry except includes the full-sibling relationship as a possibility for 1826 cM.

Sibling Matches at 23andMe

23andMe does identify full versus half-siblings.

DNAPainter disagrees with 23andMe and claims that anyone who shares 46.2% of their DNA is a parent/child.

However, look at the fine print. 23andMe counts differently than any of the other vendors, and DNAPainter relies on the Shared cM Project, which relies on testers entering known relationship matching information. Therefore, at any other vendor, DNAPainter is probably exactly right.

Before we understand how 23andMe counts, we need to understand about half versus fully identical segments.

To determine half or full siblings, 23andMe compares two things:

  1. The amount of shared matching DNA between two people
  2. Fully Identical Regions (FIR) of DNA compared to Half Identical Regions (HIR) of DNA to determine if any of your DNA is fully identical, meaning some pieces of you and your sibling’s DNA is exactly the same on both your maternal and paternal chromosomes.

Here’s an example on any chromosome – I’ve randomly selected chromosome 12. Which chromosome doesn’t matter, except for the X, which is different.

Your match isn’t broken out by maternal and paternal sides. You would simply see, on the chromosome browser, that you and your sibling match at these locations, above.

In reality, though, you have two copies of each chromosome, one from Mom and one from Dad, and so does your sibling.

In this example, Mom’s chromosome is visualized on top, and Dad’s is on the bottom, below, but as a tester, you don’t know that. All you know is that you match your sibling on all of those blue areas, above.

However, what’s actually happening in this example is that you are matching your sibling on parts of your mother’s chromosome and parts of your father’s chromosome, shown above as green areas

23andMe looks at both copies of your chromosome, the one you inherited from Mom, on top, and Dad, on the bottom, to see if you match your sibling on BOTH your mother’s and your father’s chromosomes in that location.

I’ve boxed the green matching areas in purple where you match your sibling fully, on both parents’ chromosomes.

If you and your sibling share both parents, you will share significant amounts of the same DNA on both copies of the same chromosomes, meaning maternal and paternal. In other words, full siblings share some purple fully identical regions (FIR) of DNA with each other, while half-siblings do not (unless they are also otherwise related) because half-siblings only share one parent with each other. Their DNA can’t be fully identical because they have a different parent that contributed the other copy of their chromosome.

Total Shared DNA Fully Identical DNA from Both Parents
Full Siblings ~50% ~25%
Half Siblings ~25% 0
  • Full siblings are expected to share about 50% of the same DNA. In other words, their DNA will match at that location. That’s all the green boxed locations, above.
  • Full siblings are expected to share about 25% of the same DNA from BOTH parents at the same location on BOTH copies of their chromosomes. These are fully identical regions and are boxed in purple, above.

You’ll find fully identical segments about 25% of the time in full siblings, but you won’t find fully identical segments in half-siblings. Please note that there are exceptions for ¾ siblings and endogamous populations.

You can view each match at 23andMe to see if you have any completely identical regions, shown in dark purple in the top comparison of full siblings. Half siblings are shown in the second example, with less total matching DNA and no FIR or completely identical regions.

Please note that your matching amount of DNA will probably be higher at 23andMe than at other companies because:

  • 23andMe includes the X chromosome in the match totals
  • 23andMe counts fully identical matching regions twice. For full siblings, that’s an additional 25%

Therefore, a full sibling with an X match will have a higher total cM at 23andMe than the same siblings elsewhere because not only is the X added into the total, the FIR match region is added a second time too.

Fully Identical Regions (FIR) and Half Identical Regions (HIR) at GEDmatch

At GEDMatch, you can compare two people to each other, with an option to display the matching information and a painted graphic for each chromosome that includes FIR and HIR.

If you need to know if you and a match share fully identical regions and you haven’t tested at 23andMe, you can both upload your DNA data file to GEDmatch and use their One to One Autosomal DNA Comparison.

On the following page, simply enter both kit numbers and accept the defaults, making sure you have selected one of the graphics options.

While GEDmatch doesn’t specifically tell you whether someone is a full or half sibling, you can garner additional information about the relationship based on the graphic at GEDmatch.

GEDMatch shows both half and fully identical regions.

The above match is between two full siblings using a 7 cM threshold. The blue on the bottom bar indicates a match of 7 cM or larger. Black means no match.

The green regions in the top bar indicate places where these two people carry the same DNA on both copies of their chromosome 1. This means that both people inherited the same DNA from BOTH parents on the green segments.

In the yellow regions, the siblings inherited the same DNA from ONE parent, but different DNA in that region from the other parent. They do match each other, just on one of their chromosomes, not both.

Without a tool like this to differentiate between HIR and FIR, you can’t tell if you’re matching someone on one copy of your chromosome, or on both copies.

In the areas marked with red on top, which corresponds to the black on the bottom band, these two siblings don’t match each other because they inherited different DNA from both parents in that region. The yellow in that region is too scattered to be significant.

Full siblings generally share a significant amount of FIR, or fully identical regions of DNA – about 25%.

Half siblings will share NO significant amount of FIR, although some will be FIR on very small, scattered green segments simply by chance, as you can see in the example, below.

This half-sibling match shares no segments large enough to be a match (7 cM) in the black section. In the blue matching section, only a few small green fragments of DNA match fully, which, based on the rest of that matching segment, must be identical by chance or misreads. There are no significant contiguous segments of fully identical DNA.

When dealing with full or half-siblings, you’re not interested in small, scattered segments of fully identical regions, like those green snippets on chromosome 6, but in large contiguous sections of matching DNA like the chromosome 1 example.

GEDmatch can help when you match when a vendor does not provide FIR/HIR information, and you need additional assistance.

Next, let’s look at full and half-siblings at FamilyTreeDNA

Sibling Matches at FamilyTreeDNA

FamilyTreeDNA does identify full siblings.

Relationships other than full siblings are indicated by a range. The two individuals below are both half-sibling matches to the tester.

The full range when mousing over the relationship ranges is shown below.

DNAPainter agrees except also gives full siblings as an option for the two half-siblings.

FamilyTreeDNA also tells you if you have an X match and the size of your X match.

We will talk about X matching in a minute, which, when dealing with sibling identification, can turn out to be very important.

Sibling Matches at MyHeritage

MyHeritage indicates brother or sister for full siblings

MyHeritage provides other “Estimated relationships” for matches too small to be full siblings.

DNAPainter’s chart agrees with this classification, except adds additional relationship possibilities.

Be sure to review all of the information provided by each vendor for close relationships.

View Close Known Relationships

The next easiest step to take is to compare your full or half-sibling match to known close family members from your maternal and paternal sides, respectively. The closer the family members, the better.

It’s often not possible to determine if someone is a half sibling or a full sibling by centiMorgans (cMs) alone, especially if you’re searching for unknown family members.

Let’s start with the simplest situation first.

Let’s say both of your parents have tested, and of course, you match both of them as parents.

Your new “very close match” is in the sibling range.

The first thing to do at each vendor is to utilize that vendor’s shared matches tool and see whether your new match matches one parent, or both.

Here’s an example.

Close Relationships at FamilyTreeDNA

This person has a full sibling match, but let’s say they don’t know who this is and wants to see if their new sibling matches one or both of their parents.

Select the match by checking the box to the left of the match name, then click on the little two-person icon at far right, which shows “In Common” matches

You can see on the resulting shared match list that both of the tester’s parents are shown on the shared match list.

Now let’s make this a little more difficult.

No Parents, No Problem

Let’s say neither of your parents has tested.

If you know who your family is and can identify your matches, you can see if the sibling you match matches other close relatives on both or either side of your family.

You’ll want to view shared matches with your closest known match on both sides of your tree, beginning with the closest first. Aunts, uncles, first cousins, etc.

You will match all of your family members through second cousins, and 90% of your third cousins. You can view additional relationship percentages in the article, How Much of Them is in You?.

I recommend, for this matching purpose, to utilize 2nd cousins and closer. That way you know for sure if you don’t share them as a match with your sibling, it’s because the sibling is not related on that side of the family, not because they simply don’t share any DNA due to their distance.

In this example, you have three sibling matches. Based on your and their matches to the same known first and second cousins, you can see that:

  • Sibling 1 is your full sibling, because you both match the same maternal and paternal first and second cousins
  • Sibling 2 is your paternal half-sibling because you both match paternal second cousins and closer, but not maternal cousins.
  • Sibling 3 is your maternal half-sibling because you both match maternal second cousins and closer, but not paternal cousins.

Close Relationships at Ancestry

Neither of my parents have tested, but my first cousin on my mother’s side has. Let’s say I have a suspected sibling or half-sibling match, so I click on the match’s name, then on Shared Matches.

Sure enough, my new match also matches my first cousin that I’ve labeled as “on my mother’s side.”

If my new match in the sibling range also matches my second cousins or closer on my father’s side, the new match is a full sibling, not a half-sibling.

Close Relationships at MyHeritage

Comparing my closest match provided a real surprise. I wonder if I’ve found a half-sibling to my mother.

Now, THIS is interesting.

Hmmm. More research is needed, beginning with the age of my match. MyHeritage provides ages if the MyHeritage member authorizes that information to be shared.

Close Relationships at 23andMe

Under DNA Relatives, click on your suspected sibling match, then scroll down and select “Find Relatives in Common.”

The Relatives in Common list shows people that match both of you.

The first common match is very close and a similar relationship to my closest match on my father’s side. This would be expected of a sibling. I have no common matches with this match to anyone on my mother’s side, so they are only related on my father’s side. Therefore they are a paternal half-sibling, not a full sibling.

More Tools Are Available

Hopefully, by now, you’ve been able to determine if your mystery match is a sibling, and if so, if they are a half or full sibling, and through which parent.

We have some additional tools that are relevant and can be very informative in some circumstances. I suggest utilizing these tools, even if you think you know the answer.

In this type of situation, there’s no such thing as too much information.

X Matching

X matching, or lack thereof, may help you determine how you are related to someone.

There are two types of autosomal DNA. The X chromosome versus chromosomes 1-22. The X chromosome (number 23) has a unique inheritance path that distinguishes it from your other chromosomes.

The X chromosome inheritance path also differs between men and women.

Here’s my pedigree chart in fan form, highlighting the ancestors who may have contributed a portion of their X chromosome to me. In the closest generation, this shows that I inherited an X chromosome from both of my parents, and who in each of their lines could have contributed an X to them.

The white or uncolored positions, meaning ancestors, cannot contribute any portion of an X chromosome to me based on how the X chromosome is inherited.

You’ll notice that my father inherited none of his X chromosome from any of his paternal ancestors, so of course, I can’t inherit what he didn’t inherit. There are a very limited number of ancestors on my father’s side whom I can inherit any portion of an X chromosome from.

Men receive their Y chromosome from their fathers, so men ONLY receive an X chromosome from their mother.

Therefore, men MUST pass their mother’s X chromosome on to their female offspring because they don’t have any other copy of the X chromosome to pass on.

Men pass no X chromosome to sons.

We don’t need to worry about a full fan chart when dealing with siblings and half-siblings.

We only need to be concerned with the testers plus one generation (parents) when utilizing the X chromosome in sibling situations.

These two female Disney Princesses, above, are full siblings, and both inherited an X chromosome from BOTH their mother and father. However, their father only has one X (red) chromosome to give them, so the two females MUST match on the entire red X chromosome from their father.

Their mother has two X chromosomes, green and black, to contribute – one from each of her parents.

The full siblings, Melody, and Cinderella:

  • May have inherited some portion of the same green and black X chromosomes from their mother, so they are partial matches on their mother’s X chromosome.
  • May have inherited the exact same full X chromosome from their mother (both inherited the entire green or both inherited the entire black), so they match fully on their mother’s X chromosome.
  • May have inherited the opposite X from different maternal grandparents. One inherited the entire green X and one inherited the entire black X, so they don’t match on their mother’s X chromosome.

Now, let’s look at Cinderella, who matches Henry.

This female and male full sibling match can’t share an X chromosome on the father’s side, because the male’s father doesn’t contribute an X chromosome to him. The son, Henry, inherited a Y chromosome instead from his father, which is what made them males.

Therefore, if a male and female match on the X chromosome, it MUST be through HIS mother, but could be through either of her parents. In a sibling situation, an X match between a male and female always indicates the mother.

In the example above, the two people share both of their mother’s X chromosomes, so are definitely (at least) maternally related. They could be full siblings, but we can’t determine that by the X chromosome in this situation, with males.

However, if the male matches the female on HER father’s X chromosome, there a different message, example below.

You can see that the male is related to the female on her father’s side, where she inherited the entire magenta X chromosome. The male inherited a portion of the magenta X chromosome from his mother, so these two people do have an X match. However, he matches on his mother’s side, and she matches on her father’s side, so that’s clearly not the same parent.

  • These people CAN NOT be full siblings because they don’t match on HER mother’s side too, which would also be his mother’s side if they were full siblings.
  • They cannot be maternal half-siblings because their X DNA only matches on her father’s side, but they wouldn’t know that unless she knew which side was which based on share matches.
  • They cannot be paternal half-siblings because he does not have an X chromosome from his father.

They could, however, be uncle/aunt-niece/nephew or first cousins on his mother’s side and her father’s side. (Yes, you’re definitely going to have to read this again if you ever need male-female X matching.)

Now, let’s look at X chromosome matching between two males. It’s a lot less complicated and much more succinct.

Neither male has inherited an X chromosome from their father, so if two males DO match on the X, it MUST be through their mother. In terms of siblings, this would mean they share the same mother.

However, there is one slight twist. In the above example, you can see that the men inherited a different proportion of the green and black X chromosomes from their common mother. However, it is possible that the mother could contribute her entire green X chromosome to one son, Justin in this example, and her entire black X chromosome to Henry.

Therefore, even though Henry and Justin DO share a mother, their X chromosome would NOT match in this scenario. This is rare but does occasionally happen.

Based on the above examples, the X chromosome may be relevant in the identification of full or half siblings based on the sexes of the two people who otherwise match at a level indicating a full or half-sibling relationship.

Here’s a summary chart for sibling X matching.

X Match Female Male
Female Will match on shared father’s full X chromosome, mother’s X is the same rules as chromosomes 1-22 Match through male’s mother, but either of female’s parents. If the X match is not through the female’s mother, they are not full siblings nor maternal half-siblings. They cannot have an X match through the male’s father. They are either full or half-siblings through their mother if they match on both of their mother’s side. If they match on his mother’s side, and her father’s side, they are not siblings but could be otherwise closely related.
Male Match through male’s mother, but either of female’s parents. If the X match is not through the female’s mother, they are not full siblings nor maternal half-siblings. They cannot have an X match through the male’s father. They are either full or half-siblings through their mother if they match on both or their mother’s side. If they match on his mother’s side, and her father’s side, they are not siblings but could be otherwise closely related. Both males are related on their mother’s side – either full or half-siblings.

Here’s the information presented in a different way.

DOES match X summary:

  • If a male DOES match a female on the X, he IS related to her through HIS mother’s side, but could match her on her mother or father’s side. If their match is not through her mother, then they are not full siblings nor maternal half-siblings. They cannot match through his father, so they cannot be paternal half-siblings.
  • If a female DOES match a female on the X, they could be related on either side and could be full or half-siblings.
  • If a male DOES match a male on the X, they ARE both related through their mother. They may also be related on their father’s side, but the X does not inform us of that.

Does NOT match X summary:

  • If a male does NOT match a female on the X, they are NOT related through HIS mother and are neither full siblings nor maternal half-siblings. Since a male does not have an X chromosome from his father, they cannot be paternal half-siblings based on an X match.
  • If a male does NOT match a male, they do NOT share a mother.
  • If a female does NOT match another female on the X, they are NOT full siblings and are NOT half-siblings on their paternal side. Their father only has one X chromosome, and he would have given the same X to both daughters.

Of the four autosomal vendors, only 23andMe and FamilyTreeDNA report X chromosome results and matching, although the other two vendors, MyHeritage and Ancestry, include the X in their DNA download file so you can find X matches with those files at either FamilyTreeDNA or GEDMatch if your match has or will upload their file to either of those vendors. I wrote step-by-step detailed download/upload instructions, here.

X Matching at FamilyTreeDNA

In this example from FamilyTreeDNA, the female tester has discovered two half-sibling matches, both through her father. In the first scenario, she matches a female on the full X chromosome (181 cM). She and her half-sibling MUST share their father’s entire X chromosome because he only had one X, from his mother, to contribute to both of his daughters.

In the second match to a male half-sibling, our female tester shares NO X match because her father did not contribute an X chromosome to his son.

If we didn’t know which parents these half-sibling matches were through, we can infer from the X matching alone that the male is probably NOT through the mother.

Then by comparing shared matches with each sibling, Advanced Matches, or viewing the match Matrix, we can determine if the siblings match each other and are from the same or different sides of the family.

Under Additional Tests and Tools, Advanced Matching, FamilyTreeDNA provides an additional tool that can show only X matches combined with relationships.

Of course, you’ll need to view shared matches to see which people match the mother and/or match the father.

To see who matches each other, you’ll need to use the Matrix tool.

At FamilyTreeDNA, the Matrix, located under Autosomal DNA Results and Tools, allows you to select your matches to see if they also match each other. If you have known half-siblings, or close relatives, this is another way to view relationships.

Here’s an example using my father and two paternal half-siblings. We can see that the half-siblings also match each other, so they are (at least) half-siblings on the paternal side too.

If they also matched my mother, we would be full siblings, of course.

Next, let’s use Y DNA and mitochondrial DNA.

Y DNA and Mitochondrial DNA

In addition to autosomal DNA, we can utilize Y DNA and mitochondrial DNA (mtDNA) in some cases to identify siblings or to narrow or eliminate relationship possibilities.

Given that Y DNA and mitochondrial DNA both have distinctive inheritance paths, full and half-siblings will, or will not, match under various circumstances.

Y DNA

Y DNA is passed intact from father to son, meaning it’s not admixed with any of the mother’s DNA. Daughters do not inherit Y DNA from their father, so Y DNA is only useful for male-to-male comparisons.

Two types of Y DNA are used for genealogy, STR markers for matching, and haplogroups, and both are equally powerful in slightly different ways.

Y DNA at FamilyTreeDNA

Men can order either 37 or 111 STR marker tests, or the BIg Y which provides more than 700 markers and more. FamilyTreeDNA is the only one of the vendors to offer Y DNA testing that includes STR markers and matching between men.

Men who order these tests will be compared for matching on either 37, 111 or 700 STR markers in addition to SNP markers used for haplogroup identification and assignment.

Fathers will certainly match their sons, and paternal line brothers will match each other, but they will also match people more distantly related.

However, if two men are NOT either full or half siblings on the paternal side, they won’t match at 111 markers.

If two men DON’T match, especially at high marker levels, they likely aren’t siblings. The word “likely” is in there because, very occasionally, a large deletion occurs that prevents STR matching, especially at lower levels.

Additionally, men who take the 37 or 111 marker test also receive an estimated haplogroup at a high level for free, without any additional testing.

However, if men take the Big Y-700 test, they not only will (or won’t) match on up to 700 STR markers, they will also receive a VERY refined haplogroup via SNP marker testing that is often even more sensitive in terms of matching than STR markers. Between these two types of markers, Y DNA testing can place men very granularly in relation to other men.

Men can match in two ways on Y DNA, and the results are very enlightening.

If two men match on BOTH their most refined haplogroup (Big Y test) AND STR markers, they could certainly be siblings or father/son. They could also be related on the same line for another reason, such as known or unknown cousins or closer relationships like uncle/nephew. Of course, Y DNA, in addition to autosomal matching, is a powerful combination.

Conversely, if two men don’t have a similar or close haplogroup, they are not a father and son or paternal line siblings.

FamilyTreeDNA offers both inexpensive entry-level testing (37 and 111 markers) and highly refined advanced testing of most of the Y chromosome (Big Y-700), so haplogroup assignments can vary widely based on the test you take. This makes haplogroup matching and interpretation a bit more complex.

For example, haplogroups R-M269 and I-BY14000 are not related in thousands of years. One is haplogroup R, and one is haplogroup I – completely different branches of the Y DNA tree. These two men won’t match on STR markers or their haplogroup.

However, because FamilyTreeDNA provides over 50,000 different haplogroups, or tree branches, for Big Y testers, and they provide VERY granular matching, two father/son or sibling males who have BOTH tested at the Big Y-700 level will have either the exact same haplogroup, or at most, one branch difference on the tree if a mutation occurred between father and son.

If both men have NOT tested at the Big Y-700 level, their haplogroups will be on the same branch. For example, a man who has only taken a 37/111 marker STR test may be estimated at R-M269, which is certainly accurate as far as it goes.

His sibling who has taken a Big Y test will be many branches further downstream on the tree – but on the same large haplogroup R-M269 branch. It’s essential to pay attention to which tests a Y DNA match has taken when analyzing the match.

The beauty of the two kinds of tests is that even if one haplogroup is very general due to no Big Y test, their STR markers should still match. It’s just that sometimes this means that one hand is tied behind your back.

Y DNA matching alone can eliminate the possibility of a direct paternal line connection, but it cannot prove siblingship or paternity alone – not without additional information.

The Advanced Matching tool will provide a list of matches in all categories selected – in this case, both the 111 markers and the Family Finder test. You can see that one of these men is the father of the tester, and one is the full sibling.

You can view haplogroup assignments on the public Y DNA tree, here. I wrote about using the public tree, here.

In addition, recently, FamilyTreeDNA launched the new Y DNA Discover tool, which explains more about haplogroups, including their ages and other fun facts like migration paths along with notable and ancient connections. I wrote about using the Discover tool, here.

Y DNA at 23andMe

Testers receive a base haplogroup with their autosomal test. 23andMe tests a limited number of Y DNA SNP locations, but they don’t test many, and they don’t test STR markers, so there is no Y DNA matching and no refined haplogroups.

You can view the haplogroups of your matches. If your male sibling match does NOT share the same haplogroup, the two men are not paternal line siblings. If two men DO share the same haplogroup, they MIGHT be paternal siblings. They also might not.

Again, autosomal close matching plus haplogroup comparisons include or exclude paternal side siblings for males.

Paternal side siblings at 23andMe share the same haplogroup, but so do many other people. These two men could be siblings. The haplogroups don’t exclude that possibility. If the haplogroups were different, that would exclude being either full or paternal half-siblings.

Men can also compare their mitochondrial DNA to eliminate a maternal relationship.

These men are not full siblings or maternal half-siblings. We know, unquestionably, because their mitochondrial haplogroups don’t match.

23andMe also constructs a genetic tree, but often struggles with close relative placement, especially when half-relationships are involved. I do not recommend relying on the genetic tree in this circumstance.

Mitochondrial DNA

Mitochondrial DNA is passed from mothers to all of their children, but only females pass it on. If two people, males or females, don’t match on their mitochondrial DNA test, with a couple of possible exceptions, they are NOT full siblings, and they are NOT maternal half-siblings.

Mitochondrial DNA at 23andMe

23andMe provides limited, base mitochondrial haplogroups, but no matching. If two people don’t have the same haplogroup at 23andMe, they aren’t full or maternal siblings, as illustrated above.

Mitochondrial DNA at FamilyTreeDNA

FamilyTreeDNA provides both mitochondrial matching AND a much more refined haplogroup. The full sequence test (mtFull), the only version sold today, is essential for reliable comparisons.

Full siblings or maternal half-siblings will always share the same haplogroup, regardless of their sex.

Generally, a full sibling or maternal half-sibling match will match exactly at the full mitochondrial sequence (FMS) level with a genetic distance of zero, meaning fully matching and no mismatching mutations.

There are rare instances where maternal siblings or even mothers and children do not match exactly, meaning they have a genetic distance of greater than 0, because of a mutation called a heteroplasmy.

I wrote about heteroplasmies, here.

Like Y DNA, mitochondrial DNA cannot identify a sibling or parental relationship without additional evidence, but it can exclude one, and it can also provide much-needed evidence in conjunction with autosomal matching. The great news is that unlike Y DNA, everyone has mitochondrial DNA and it comes directly from their mother.

Once again, FamilyTreeDNA’s Advanced Matching tool provides a list of people who match you on both your mitochondrial DNA test and the Family Finder autosomal test, including transfers/uploads, and provides a relationship.

You can see that our tester matches both a full sibling and their mother. Of course, a parent/child match could mean that our tester is a female and one of her children, of either sex, has tested.

Below is an example of a parent-child match that has experienced a heteroplasmy.

Based on the comparison of both the mitochondrial DNA test, plus the autosomal Family Finder test, you can verify that this is a close family relationship.

You can also eliminate potential relationships based on the mitochondrial DNA inheritance path. The mitochondrial DNA of full siblings and maternal half-siblings will always match at the full sequence and haplogroup level, and paternal half-siblings will never match. If paternal half-siblings do match, it’s happenstance or because of a different reason.

Sibling Summary and Checklist

I’ve created a quick reference checklist for you to use when attempting to determine whether or not a match is a sibling, and, if so, whether they are half or full siblings. Of course, these tools are in addition to the DNAPainter Shared cM Tool and GEDmatch’s Relationship Predictor Calculator.

FamilyTreeDNA Ancestry 23andMe MyHeritage GEDmatch
Matching Yes Yes Yes Yes Yes
Shared Matches Yes – In Common With Yes – Shared Matches Yes – Relatives in Common Yes – Review DNA Match Yes – People who match both or 1 of 2 kits
Relationship Between Shared Matches No No No Yes, under shared match No
Matches Match Each Other* Yes, Matrix No Yes, under “View DNA details,” then, “compare with more relatives” Partly, through triangulation Yes, can match any kits
Full Siblings Yes Sibling, implies full Yes Brother, Sister, means full No
Half Siblings Sibling, Uncle/Aunt-Niece/Nephew, Grandparent-Grandchild Close Family – 1C Yes Half sibling, aunt/uncle-niece-nephew No
Fully Identical Regions (FIR) No No Yes No Yes
Half Identical Regions (HIR) No No Yes No Yes
X matching Yes No Yes No Yes
Unusual Reporting or Anomalies No No, Timber is not used on close relationships X match added into total, FIR added twice No Matching amount can vary from vendors
Y DNA Yes, STRs, refined haplogroups, matching No High-level haplogroup only, no matching No No, only if tester enters haplogroup manually
Mitochondrial DNA Yes, full sequence, matching, refined haplogroup No High-level haplogroup only, no matching No No, only if tester enters haplogroup manually
Combined Tools (Autosomal, X, Y, mtDNA) Yes No No No No

*Autoclusters through Genetic Affairs show cluster relationships of matches to the tester and to each other, but not all matches are included, including close matches. While this is a great tool, it’s not relevant for determining close and sibling relationships. See the article, AutoClustering by Genetic Affairs, here.

Additional Resources

Some of you may be wondering how endogamy affects sibling numbers.

Endogamy makes almost everything a little more complex. I wrote about endogamy and various ways to determine if you have an endogamous heritage, here.

Please note that half-siblings with high cM matches also fall into the range of full siblings (1613-3488), with or without endogamy. This may be, but is not always, especially pronounced in endogamous groups.

As another resource, I wrote an earlier article, Full or Half Siblings, here, that includes some different examples.

Strategy

You have a lot of quills in your quiver now, and I wish you the best if you’re trying to unravel a siblingship mystery.

You may not know who your biological family is, or maybe your sibling doesn’t know who their family is, but perhaps your close relatives know who their family is and can help. Remember, the situation that has revealed itself may be a shock to everyone involved.

Above all, be kind and take things slow. If your unexpected sibling match becomes frightened or overwhelmed, they may simply check out and either delete their DNA results altogether or block you. They may have that reaction before you have a chance to do anything.

Because of that possibility, I recommend performing your analysis quickly, along with taking relevant screenshots before reaching out so you will at least have that much information to work with, just in case things go belly up.

When you’re ready to make contact, I suggest beginning by sending a friendly, short, message saying that you’ve noticed that you have a close match (don’t say sibling) and asking what they know about their family genealogy – maybe ask who their grandparents are or if they have family living in the area where you live. I recommend including a little bit of information about yourself, such as where you were born and are from.

I also refrain from using the word adoption (or similar) in the beginning or giving too much detailed information, because it sometimes frightens people, especially if they know or discover that there’s a painful or embarrassing family situation.

And, please, never, ever assume the worst of anyone or their motives. They may be sitting at their keyboard with the same shocked look on their face as you – especially if they have, or had, no idea. They may need space and time to reach a place of acceptance. There’s just nothing more emotionally boat-capsizing in your life than discovering intimate and personal details about your parents, one or both, especially if that discovery is disappointing and image-altering.

Or, conversely, your sibling may have been hoping and waiting just for you!

Take a deep breath and let me know how it goes!

Please feel free to share this article with anyone who could benefit.

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Top Ten RootsTech 2022 DNA Sessions + All DNA Session Links

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The official dates of RootsTech 2022 were March 3-5, but the sessions and content in the vendor booths are still available. I’ve compiled a list of the sessions focused on DNA, with web links on the RootsTech YouTube channel

YouTube reports the number of views, so I was able to compile that information as of March 8, 2022.

I do want to explain a couple of things to add context to the numbers.

Most speakers recorded their sessions, but a few offered live sessions which were recorded, then posted later for participants to view. However, there have been glitches in that process. While the sessions were anticipated to be available an hour or so later, that didn’t quite happen, and a couple still aren’t posted. I’m sure the presenters are distressed by this, so be sure to watch those when they are up and running.

The Zoom rooms where participants gathered for the live sessions were restricted to 500 attendees. The YouTube number of views does not include the number of live viewers, so you’ll need to add an additional number, up to 500.

When you see a number before the session name, whether recorded or live, that means that the session is part of a series. RootsTech required speakers to divide longer sessions into a series of shorter sessions no longer than 15-20 minutes each. The goal was for viewers to be able to watch the sessions one after the other, as one class, or separately, and still make sense of the content. Let’s just say this was the most challenging thing I’ve ever done as a presenter.

For recorded series sessions, these are posted as 1, 2 and 3, as you can see below with Diahan Southard’s sessions. However, with my live session series, that didn’t happen. It looks like my sessions are a series, but when you watch them, parts 1, 2 and 3 are recorded and presented as one session. Personally, I’m fine with this, because I think the information makes a lot more sense this way. However, it makes comparisons difficult.

This was only the second year for RootsTech to be virtual and the conference is absolutely HUGE, so live and learn. Next year will be smoother and hopefully, at least partially in-person too.

When I “arrived” to present my live session, “Associating Autosomal DNA Segments With Ancestors,” my lovely moderator, Rhett, told me that they were going to livestream my session to the RootsTech page on Facebook as well because they realized that the 500 Zoom seat limit had been a problem the day before with some popular sessions. I have about 9000 views for that session and more than 7,400 of them are on the RootsTech Facebook page – and that was WITHOUT any advance notice or advertising. I know that the Zoom room was full in addition. I felt kind of strange about including my results in the top ten because I had that advantage, but I didn’t know quite how to otherwise count my session. As it turns out, all sessions with more than 1000 views made it into the top ten so mine would have been there one way or another. A big thank you to everyone who watched!

I hope that the RootsTech team notices that the most viewed session is the one that was NOT constrained by the 500-seat limited AND was live-streamed on Facebook. Seems like this might be a great way to increase session views for everyone next year. Hint, hint!!!

I also want to say a huge thank you to all of the presenters for producing outstanding content. The sessions were challenging to find, plus RootsTech is always hectic, even virtually. So, I know a LOT of people will want to view these informative sessions, now that you know where to look and have more time. Please remember to “like” the session on YouTube as a way of thanking your presenter.

With 140 DNA-focused sessions available, you can watch a new session, and put it to use, every other day for the next year! How fun is that! You can use this article as your own playlist.

Please feel free to share this article with your friends and genealogy groups so everyone can learn more about using DNA for genealogy.

Ok, let’s look at the top 10. Drum roll please…

Top 10 Most Viewed RootsTech Sessions

Session Title Presenter YouTube Link Views
1 1. Associating Autosomal DNA Segments With Ancestors Roberta Estes (live) https://www.youtube.com/watch?v=_IHSCkNnX48

 

 ~9000: 1019 + 500 live viewers + 7,400+ Facebook
2 1. What to Do with Your DNA Test Results in 2022 (part 1 of 3) Diahan Southard https://www.youtube.com/watch?v=FENAKAYLXX4 7428
3 Who Is FamilyTreeDNA? FamilyTreeDNA – Bennett Greenspan https://www.youtube.com/watch?v=MHFtwoatJ-A 2946
4 2. What to Do with Your DNA Test Results in 2022 (part 2 of 3) Diahan Southard https://www.youtube.com/watch?v=mIllhtONhlI 2448
5 Latest DNA Painter Releases DNAPainter Jonny Perl (live) https://www.youtube.com/watch?v=iLBThU8l33o 2230 + live viewers
6 DNA Painter Introduction DNAPainter – Jonny Perl https://www.youtube.com/watch?v=Rpe5LMPNmf0 1983
7 3. What to Do with Your DNA Test Results in 2022 (part 3 of 3) Diahan Southard https://www.youtube.com/watch?v=hemY5TuLmGI 1780
8 The Tree of Mankind Age Estimates Paul Maier https://www.youtube.com/watch?v=jjkL8PWAEwk 1638
9 A Sneak Peek at FamilyTreeDNA Coming Attractions FamilyTreeDNA (live) https://www.youtube.com/watch?v=K9sKqNScvnE 1270 + live viewers

 
10 Extending Time Horizons with DNA Rob Spencer (live) https://www.youtube.com/watch?v=wppXD1Zz2sQ 1037 + live viewers

 

All DNA-Focused Sessions

I know you’ll find LOTS of goodies here. Which ones are your favorites?

  Session Presenter YouTube Link Views
1 Estimating Relationships by Combining DNA from Multiple Siblings Amy Williams https://www.youtube.com/watch?v=xs1U0ohpKSA 201
2 Overview of HAPI-DNA.org Amy Williams https://www.youtube.com/watch?v=FjNiJgWaBeQ 126
3 How do AncestryDNA® Communities help tell your story? | Ancestry® Ancestry https://www.youtube.com/watch?v=EQNpUxonQO4 183

 
4 AncestryDNA® 201 Ancestry – Crista Cowan https://www.youtube.com/watch?v=lbqpnXloM5s

 

 494
5 Genealogy in a Minute: Increase Discoveries by Attaching AncestryDNA® Results to Family Tree Ancestry – Crista Cowan https://www.youtube.com/watch?v=iAqwSCO8Pvw 369
6 AncestryDNA® 101: Beginner’s Guide to AncestryDNA® | Ancestry® Ancestry – Lisa Elzey https://www.youtube.com/watch?v=-N2usCR86sY 909
7 Hidden in Plain Sight: Free People of Color in Your Family Tree Cheri Daniels https://www.youtube.com/watch?v=FUOcdhO3uDM 179
8 Finding Relatives to Prevent Hereditary Cancer ConnectMyVariant – Dr. Brian Shirts https://www.youtube.com/watch?v=LpwLGgEp2IE 63
9 Piling on the chromosomes Debbie Kennett https://www.youtube.com/watch?v=e14lMsS3rcY 465
10 Linking Families With Rare Genetic Condition Using Genealogy Deborah Neklason https://www.youtube.com/watch?v=b94lUfeAw9k 43
11 1. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=FENAKAYLXX4 7428
12 1. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=hemY5TuLmGI 1780
13 2. What to Do with Your DNA Test Results in 2022 Diahan Southard https://www.youtube.com/watch?v=mIllhtONhlI 2448
14 DNA Testing For Family History Diahan Southard https://www.youtube.com/watch?v=kCLuOCC924s 84

 
15 Understanding Your DNA Ethnicity Estimate at 23andMe Diana Elder

 

 https://www.youtube.com/watch?v=xT1OtyvbVHE 66
16 Understanding Your Ethnicity Estimate at FamilyTreeDNA Diana Elder https://www.youtube.com/watch?v=XosjViloVE0 73
17 DNA Monkey Wrenches Katherine Borges https://www.youtube.com/watch?v=Thv79pmII5M 245
18 Advanced Features in your Ancestral Tree and Fan Chart DNAPainter – Jonny Perl https://www.youtube.com/watch?v=4u5Vf13ZoAc 425
19 DNA Painter Introduction DNAPainter – Jonny Perl https://www.youtube.com/watch?v=Rpe5LMPNmf0 1983
20 Getting Segment Data from 23andMe DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=8EBRI85P3KQ 134
21 Getting segment data from FamilyTreeDNA DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=rWnxK86a12U 169
22 Getting segment data from Gedmatch DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=WF11HEL8Apk 163
23 Getting segment data from Geneanet DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=eclj8Ap0uK4 38
24 Getting segment data from MyHeritage DNA matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=9rGwOtqbg5E 160
25 Inferred Chromosome Mapping: Maximize your DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=tzd5arHkv64 688
26 Keeping track of your genetic family tree in a fan chart DNAPainter – Jonny Perl https://www.youtube.com/watch?v=W3Hcno7en94 806

 
27 Mapping a DNA Match in a Chromosome Map DNAPainter – Jonny Perl https://www.youtube.com/watch?v=A61zQFBWaiY 423
28 Setting up an Ancestral Tree and Fan Chart and Exploring Tree Completeness DNAPainter – Jonny Perl https://www.youtube.com/watch?v=lkJp5Xk1thg 77
29 Using the Shared cM Project Tool to Evaluate DNA Matches DNAPainter – Jonny Perl https://www.youtube.com/watch?v=vxhn9l3Dxg4 763
30 Your First Chromosome Map: Using your DNA Matches to Link Segments to Ancestors DNAPainter – Jonny Perl https://www.youtube.com/watch?v=tzd5arHkv64 688
31 DNA Painter for absolute beginners DNAPainter (Jonny Perl) https://www.youtube.com/watch?v=JwUWW4WHwhk 1196
32 Latest DNA Painter Releases DNAPainter (live) https://www.youtube.com/watch?v=iLBThU8l33o 2230 + live viewers
33 Unraveling your genealogy with DNA segment networks using AutoSegment from Genetic Affairs Evert-Jan Blom https://www.youtube.com/watch?v=rVpsJSqOJZI

 

 162
34 Unraveling your genealogy with genetic networks using AutoCluster Evert-Jan Blom https://www.youtube.com/watch?v=ZTKSz_X7_zs 201

 

 
35 Unraveling your genealogy with reconstructed trees using AutoTree & AutoKinship from Genetic Affairs Evert-Jan Blom https://www.youtube.com/watch?v=OmDQoAn9tVw 143
36 Research Like a Pro with DNA – A Genealogist’s Guide to Finding and Confirming Ancestors with DNA Family Locket Genealogists https://www.youtube.com/watch?v=NYpLscJJQyk 183
37 How to Interpret a DNA Network Graph Family Locket Genealogists – Diana Elder https://www.youtube.com/watch?v=i83WRl1uLWY 393
38 Find and Confirm Ancestors with DNA Evidence Family Locket Genealogists – Nicole Dyer https://www.youtube.com/watch?v=DGLpV3aNuZI 144
39 How To Make A DNA Network Graph Family Locket Genealogists – Nicole Dyer https://www.youtube.com/watch?v=MLm_dVK2kAA 201
40 Create A Family Tree With Your DNA Matches-Use Lucidchart To Create A Picture Worth A Thousand Words Family Locket Genealogists – Robin Wirthlin https://www.youtube.com/watch?v=RlRIzcW-JI4 270
41 Charting Companion 7 – DNA Edition Family Tree Maker https://www.youtube.com/watch?v=k2r9rkk22nU 316

 
42 Family Finder Chromosome Browser: How to Use FamilyTreeDNA https://www.youtube.com/watch?v=w0_tgopBn_o 750

 

 
43 FamilyTreeDNA: 22 Years of Breaking Down Brick Walls FamilyTreeDNA https://www.familysearch.org/rootstech/session/familytreedna-22-years-of-breaking-down-brick-walls Not available
44 Review of Autosomal DNA, Y-DNA, & mtDNA FamilyTreeDNA  – Janine Cloud https://www.youtube.com/watch?v=EJoQVKxgaVY 77
45 Who Is FamilyTreeDNA? FamilyTreeDNA – Bennett Greenspan https://www.youtube.com/watch?v=MHFtwoatJ-A 2946
46 Part 1: How to Interpret Y-DNA Results, A Walk Through the Big Y FamilyTreeDNA – Casimir Roman https://www.youtube.com/watch?v=ra1cjGgvhRw 684

 
47 Part 2: How to Interpret Y-DNA Results, A Walk Through the Big Y FamilyTreeDNA – Casimir Roman https://www.youtube.com/watch?v=CgqcjBD6N8Y

 

 259
48 Big Y-700: A Brief Overview FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=IefUipZcLCQ 96
49 Mitochondrial DNA & The Million Mito Project FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=5Zppv2uAa6I 179
50 Mitochondrial DNA: What is a Heteroplasmy FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=ZeGTyUDKySk 57
51 Y-DNA Big Y: A Lifetime Analysis FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=E6NEU92rpiM 154
52 Y-DNA: How SNPs Are Added to the Y Haplotree FamilyTreeDNA – Janine Cloud https://www.youtube.com/watch?v=CGQaYcroRwY 220
53 Family Finder myOrigins: Beginner’s Guide FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=VrJNpSv8nlA 88
54 Mitochondrial DNA: Matches Map & Results for mtDNA FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=YtA1j01MOvs 190
55 Mitochondrial DNA: mtDNA Mutations Explained FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=awPs0cmZApE 340

 
56 Y-DNA: Haplotree and SNPs Page Overview FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=FOuVhoMD-hw 432
57 Y-DNA: Understanding the Y-STR Results Page FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=gCeZz1rQplI 148
58 Y-DNA: What Is Genetic Distance? FamilyTreeDNA – Katy Rowe https://www.youtube.com/watch?v=qJ6wY6ILhfg 149
59 DNA Tools: myOrigins 3.0 Explained, Part 1 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=ACgY3F4-w78 74

 
60 DNA Tools: myOrigins 3.0 Explained, Part 2 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=h7qU36bIFg0 50
61 DNA Tools: myOrigins 3.0 Explained, Part 3 FamilyTreeDNA – Paul Maier https://www.youtube.com/watch?v=SWlGPm8BGyU 36
62 African American Genealogy Research Tips FamilyTreeDNA – Sherman McRae https://www.youtube.com/watch?v=XdbkM58rXIQ 153

 
63 Connecting With My Ancestors Through Y-DNA FamilyTreeDNA – Sherman McRae https://www.youtube.com/watch?v=xbo1XnLkuQU 200
64 Join The Million Mito Project FamilyTreeDNA (Join link) https://www.familysearch.org/rootstech/session/join-the-million-mito-project link
65 View the World’s Largest mtDNA Haplotree FamilyTreeDNA (Link to mtDNA tree) https://www.familytreedna.com/public/mt-dna-haplotree/L n/a
66 View the World’s Largest Y Haplotree FamilyTreeDNA (Link to Y tree) https://www.familytreedna.com/public/y-dna-haplotree/A link
67 A Sneak Peek at FamilyTreeDNA Coming Attractions FamilyTreeDNA (live) https://www.youtube.com/watch?v=K9sKqNScvnE 1270 + live viewers

 
68 DNA Upload: How to Transfer Your Autosomal DNA Data FamilyTreeDNA -Katy Rowe https://www.youtube.com/watch?v=CS-rH_HrGlo 303
69 Family Finder myOrigins: How to Compare Origins With Your DNA Matches FamilyTreeDNA -Katy Rowe https://www.youtube.com/watch?v=7mBmWhM4j9Y 145
70 Join Group Projects at FamilyTreeDNA FamilyTreeDNA link to learning center article) https://www.familysearch.org/rootstech/session/join-group-projects-at-familytreedna link

 
71 Product Demo – Unraveling your genealogy with reconstructed trees using AutoKinship GEDmatch https://www.youtube.com/watch?v=R7_W0FM5U7c 803
72 Towards a Genetic Genealogy Driven Irish Reference Genome Gerard Corcoran https://www.youtube.com/watch?v=6Kx8qeNiVmo 155

 
73 Discovering Biological Origins in Chile With DNA: Simple Triangulation Gonzalo Alexis Luengo Orellana https://www.youtube.com/watch?v=WcVby54Uigc 40
74 Cousin Lynne: An Adoption Story International Association of Jewish Genealogical Societies https://www.youtube.com/watch?v=AptMcV4_B4o 111
75 Using DNA Testing to Uncover Native Ancestry Janine Cloud https://www.youtube.com/watch?v=edzebJXepMA 205
76 1. Forensic Genetic Genealogy Jarrett Ross https://www.youtube.com/watch?v=0euIDZTmx5g 58
77 Reunited and it Feels so Good Jennifer Mendelsohn https://www.youtube.com/watch?v=X-hxjm7grBE 57

 
78 Genealogical Research and DNA Testing: The Perfect Companions Kimberly Brown https://www.youtube.com/watch?v=X82jA3xUVXk 80
79 Finding a Jewish Sperm Donor Kitty Munson Cooper https://www.youtube.com/watch?v=iKRjFfNcpug 164
80 Using DNA in South African Genealogy Linda Farrell https://www.youtube.com/watch?v=HXkbBWmORM0 141
81 Using DNA Group Projects In Your Family History Research Mags Gaulden https://www.youtube.com/watch?v=0tX7QDib4Cw 165
82 2. The Expansion of Genealogy Into Forensics Marybeth Sciaretta https://www.youtube.com/watch?v=HcEO-rMe3Xo 35

 
83 DNA Interest Groups That Keep ’em Coming Back McKell Keeney (live) https://www.youtube.com/watch?v=HFwpmtA_QbE 180 plus live viewers
84 Searching for Close Relatives with Your DNA Results Mckell Keeney (live) https://www.familysearch.org/rootstech/session/searching-for-close-relatives-with-your-dna-results Not yet available
85 Top Ten Reasons To DNA Test For Family History Michelle Leonard https://www.youtube.com/watch?v=1B9hEeu_dic 181
86 Top Tips For Identifying DNA Matches Michelle Leonard https://www.youtube.com/watch?v=-3Oay_btNAI 306
87 Maximising Messages Michelle Patient https://www.youtube.com/watch?v=4TRmn0qzHik 442
88 How to Filter and Sort Your DNA Matches MyHeritage https://www.youtube.com/watch?v=fmIgamFDvc8 88
89 How to Get Started with Your DNA Matches MyHeritage https://www.youtube.com/watch?v=JPOzhTxhU0E 447

 
90 How to Track DNA Kits in MyHeritage` MyHeritage https://www.youtube.com/watch?v=2W0zBbkBJ5w 28

 
91 How to Upload Your DNA Data to MyHeritage MyHeritage https://www.youtube.com/watch?v=nJ4RoZOQafY 82
92 How to Use Genetic Groups MyHeritage https://www.youtube.com/watch?v=PtDAUHN-3-4 62
My Story: Hope MyHeritage https://www.youtube.com/watch?v=qjyggKZEXYA 133
93 MyHeritage Keynote, RootsTech 2022 MyHeritage https://www.familysearch.org/rootstech/session/myheritage-keynote-rootstech-2022 Not available
94 Using Labels to Name Your DNA Match List MyHeritage https://www.youtube.com/watch?v=enJjdw1xlsk 139

 
95 An Introduction to DNA on MyHeritage MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=1I6LHezMkgc 60
96 Using MyHeritage’s Advanced DNA Tools to Shed Light on Your DNA Matches MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=Pez46Xw20b4 110
97 You’ve Got DNA Matches! Now What? MyHeritage – Daniel Horowitz https://www.youtube.com/watch?v=gl3UVksA-2E 260
98 My Story: Lizzie and Ayla MyHeritage – Elizbeth Shaltz https://www.youtube.com/watch?v=NQv6C8G39Kw 147
99 My Story: Fernando and Iwen MyHeritage – Fernando Hermansson https://www.youtube.com/watch?v=98-AR0M7fFE 165

 
100 Using the Autocluster and the Chromosome Browser to Explore Your DNA Matches MyHeritage – Gal Zruhen https://www.youtube.com/watch?v=a7aQbfP7lWU 115

 
101 My Story : Kara Ashby Utah Wedding MyHeritage – Kara Ashby https://www.youtube.com/watch?v=Qbr_gg1sDRo 200
102 When Harry Met Dotty – using DNA to break down brick walls Nick David Barratt https://www.youtube.com/watch?v=8SdnLuwWpJs 679
103 How to Add a DNA Match to Airtable Nicole Dyer https://www.youtube.com/watch?v=oKxizWIOKC0 161
104 How to Download DNA Match Lists with DNAGedcom Client Nicole Dyer https://www.youtube.com/watch?v=t9zTWnwl98E 124
105 How to Know if a Matching DNA Segment is Maternal or Paternal Nicole Dyer https://www.youtube.com/watch?v=-zd5iat7pmg 161
106 DNA Basics Part I Centimorgans and Family Relationships Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=SI1yUdnSpHA 372
107 DNA Basics Part II Clustering and Connecting Your DNA Matches Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=ECs4a1hwGcs 333
108 DNA Basics Part III Charting Your DNA Matches to Get Answers Origins International, Inc. dba Origins Genealogy https://www.youtube.com/watch?v=qzybjN0JBGY 270
109 2. Using Cluster Auto Painter Patricia Coleman https://www.youtube.com/watch?v=-nfLixwxKN4 691
110 3. Using Online Irish Records Patricia Coleman https://www.youtube.com/watch?v=mZsB0l4z4os 802
111 Exploring Different Types of Clusters Patricia Coleman https://www.youtube.com/watch?v=eEZBFPC8aL4 972

 
112 The Million Mito Project: Growing the Family Tree of Womankind Paul Maier https://www.youtube.com/watch?v=cpctoeKb0Kw 541
113 The Tree of Mankind Age Estimates Paul Maier https://www.youtube.com/watch?v=jjkL8PWAEwk 1638
114 Y-DNA and Mitochondrial DNA Testing Plans Paul Woodbury https://www.youtube.com/watch?v=akymSm0QKaY 168
115 Finding Biological Family Price Genealogy https://www.youtube.com/watch?v=4xh-r3hZ6Hw 137
116 What Y-DNA Testing Can Do for You Richard Hill https://www.youtube.com/watch?v=a094YhIY4HU 191
117 Extending Time Horizons with DNA Rob Spencer (live) https://www.youtube.com/watch?v=wppXD1Zz2sQ 1037 + live viewers
118 DNA for Native American Ancestry by Roberta Estes Roberta Estes https://www.youtube.com/watch?v=EbNyXCFfp4M 212
119 1. Associating Autosomal DNA Segments With Ancestors Roberta Estes (live) https://www.youtube.com/watch?v=_IHSCkNnX48

 

 ~9000: 1019 + 500 live viewers + 7,400+ Facebook
120 1. What Can I Do With Ancestral DNA Segments? Roberta Estes (live) https://www.youtube.com/watch?v=Suv3l4iZYAQ 325 plus live viewers

 
121 Native American DNA – Ancient and Contemporary Maps Roberta Estes (live) https://www.youtube.com/watch?v=dFTl2vXUz_0 212 plus 483 live viewers

 
122 How Can DNA Enhance My Family History Research? Robin Wirthlin https://www.youtube.com/watch?v=f3KKW-U2P6w 102
123 How to Analyze a DNA Match Robin Wirthlin https://www.youtube.com/watch?v=LTL8NbpROwM 367
124 1. Jewish Ethnicity & DNA: History, Migration, Genetics Schelly Talalay Dardashti https://www.youtube.com/watch?v=AIJyphGEZTA 82

 
125 2. Jewish Ethnicity & DNA: History, Migration, Genetics Schelly Talalay Dardashti https://www.youtube.com/watch?v=VM3MCYM0hkI 72
126 Ask us about DNA Talking Family History (live) https://www.youtube.com/watch?v=kv_RfR6OPpU 96 plus live viewers
127 1. An Introduction to Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=WNhErW5UVKU

 

 183
128 2. An Introduction to Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=CRpQ8EVOShI 110

 
129 Common Problems When Doing Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=hzFxtBS5a8Y 68
130 Cross Visual Phasing to Go Back Another Generation Tanner Blair Tolman https://www.youtube.com/watch?v=MrrMqhfiwbs 64
131 DNA Basics Tanner Blair Tolman https://www.youtube.com/watch?v=OCMUz-kXNZc 155
132 DNA Painter and Visual Phasing Tanner Blair Tolman https://www.youtube.com/watch?v=2-eh1L4wOmQ 155
133 DNA Painter Part 2: Chromosome Mapping Tanner Blair Tolman https://www.youtube.com/watch?v=zgOJDRG7hJc 172
134 DNA Painter Part 3: The Inferred Segment Generator Tanner Blair Tolman https://www.youtube.com/watch?v=96ai8nM4lzo

 

 100
135 DNA Painter Part 4: The Distinct Segment Generator Tanner Blair Tolman https://www.youtube.com/watch?v=Pu-WIEQ_8vc 83
136 DNA Painter Part 5: Ancestral Trees Tanner Blair Tolman https://www.youtube.com/watch?v=dkYDeFLduKA 73
137 Understanding Your DNA Ethnicity Results Tanner Blair Tolman https://www.youtube.com/watch?v=4tAd8jK6Bgw 518
138 What’s New at GEDmatch Tim Janzen https://www.youtube.com/watch?v=AjA59BG_cF4

 

 515
139 What Does it Mean to Have Neanderthal Ancestry? Ugo Perego https://www.youtube.com/watch?v=DshCKDW07so 190
140 Big Y-700 Your DNA Guide https://www.youtube.com/watch?v=rIFC69qswiA 143
141 Next Steps with Your DNA Your DNA Guide – Diahan Southard (live) https://www.familysearch.org/rootstech/session/next-steps-with-your-dna Not yet available

Additions:

142  Adventures of an Amateur Genetic Genealogist – Geoff Nelson https://www.familysearch.org/rootstech/session/adventures-of-an-amateur-genetic-genealogist     291 views

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Shared cM Project 2020 Analysis, Comparison & Handy Reference Charts

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15

Recently, Blaine Bettinger published V4 of the Shared cM Project, and along with that, Jonny Perl at DNAPainter updated the associated interactive tool as well, including histograms. I wrote about that, here.

The goal of the shared cM project was and remains to document how much DNA can be expected to be shared by various individuals at specific relationship levels. This information allows matches to at least minimally “position” themselves in a general location their trees or conversely, to eliminate specific potential relationships.

Shared cM Project match data is gathered by testers submitting their match information through the submission portal, here.

When the Shared cM Project V3 was released in September 2017, I combined information from various sources and provided an analysis of that data, including the changes from the V2 release in 2016.

I’ve done the same thing this year, adding the new data to the previous release’s table.

Compiled Comparison Table

I initially compiled this table for myself, then decided to update it and share with my readers. This chart allows me to view various perspectives on shared data and relationships and in essence has all the data I might need, including multiple versions, in one place. Feel free to copy and save the table.

In the comparison table below, the relationship rows with data from various sources is shown as follows:

  • White – Shared cM Project 2016
  • Peach – Shared cM Project 2017
  • Purple – Shared cM Project 2020
  • Green – DNA Detectives chart

I don’t know if DNA Detectives still uses the “green chart” or if they have moved to the interactive DNAPainter tool. I’ve retained the numbers for historical reference regardless.

Additionally, in some places, you’ll see references to the “degree of relationship,” as in “third degree relatives always match each other.” I’ve included a “Degree of Relationship” column to the far right, but I don’t come across those “relationship degree” references often anymore either. However, it’s here for reference if you need it.

23andMe still gives relationships in percentages, so I’ve included the expected shared percent of DNA for each relationship and the actual shared range from the DNA Detectives Green Chart.

One column shows the expected shared cM amount, assuming that 50% of the DNA from each ancestor is passed on in each generation. Clearly, we know that inheritance doesn’t happen that cleanly because recombination is a random event and children do NOT inherit exactly half of each ancestor’s DNA carried by their parents, but the average should be someplace close to this number.

shared cm table 2020

click to open separately, then use your magnifier to enlarge

The first thing I noticed about V4 is that there is a LOT more data which means that the results are likely more accurate. V4 increased by 32K data points, or 147%. Bravo to everyone who participated, to Blaine for the analysis and to Jonny for automating the results at DNAPainter.

Methods

Blaine provided his white paper, here, which includes “everything you need to know” about the project, and I strongly encourage you to read it. Not only does this document explain the process and methods, it’s educational in its own right.

On the first page, Blaine discusses issues. Any time you are crowd sourcing information, you’re going to encounter challenges and errors. Blaine did remove any entries that were clearly problematic, plus an additional 1% of all entries for each category – .5% from each end meaning the largest and smallest entries. This was done in an attempt to remove the results most likely to be erroneous.

Known issues include:

  • Data entry errors – I refer to these as “clerical mutations,” but they happen and there is no way, unless the error is egregious, to know what is a typo and what is real. Obviously, a parent sharing only a 10 cM segment with a child is not possible, but other data entry errors are well within the realm of possible.
  • Incorrect relationships – Misreported or misunderstood relationships will skew the numbers. Relationships may be believed to be one type, but are actually something else. For example, a half vs full sibling, or a half vs full aunt or uncle.
  • Misunderstood Relationships – People sometimes become confused as to the difference between “half” and “removed” from time to time. I wrote a helpful article titled Quick Tip – Calculating Cousin Relationships Easily.
  • Endogamy – Endogamy occurs when a population intermarries within itself, meaning that the same ancestral DNA is present in many members of the community. This genetic result is that you may share more DNA with those cousins than you would otherwise share with cousins at the same distance without endogamy.
  • Pedigree Collapse – Pedigree collapse occurs when you find the same ancestors multiple times in your tree. The closer to current those ancestors appear, the more DNA you will potentially carry from those repeat ancestors. The difference between endogamy and pedigree collapse is that endogamy is a community event and pedigree collapse has only to do with your own tree. You might just have both, too.
  • Company Reporting Differences – Different companies report DNA in different ways in addition to having different matching thresholds. For example, Family Tree DNA includes in your match total all DNA to 1 cM that you share with a match over the matching threshold. Conversely, Ancestry has a lower matching threshold, but often strips out some matching DNA using Timber. 23andMe counts fully identical segments twice and reports the X chromosome in their totals. MyHeritage does not report the X chromosome. There is no “right” or “wrong,” or standardization, simply different approaches. Hopefully, the variances will be removed or smoothed in the averages.
  • Distant Cousin Relationships – While this isn’t really an issue, per se, it’s important to understand what is being reported beyond 2nd cousin relationships in that the only relationships used to calculate these averages is the DNA from people who DO share DNA with their more distant cousins. In other words, if you do NOT match your 3rd cousin, then your “0” shared DNA is not included in the average. Only those who do match have their matching amounts included. This means that the average is only the average of people who match, not the average of all 3rd cousins.

Challenges aside, the Shared cM Project provides genealogists with a wonderful opportunity to use the combined data of tens of thousands of relationships to estimate and better understand the relationship range of our matches.

The Shared cM Project in combination with DNAPainter provides us with a wonderful tool.

Histograms

When analyzing the data, one of the first things I noticed was a very unusual entry for parent/child relationships.

We all know that children each inherit exactly half of their parent’s DNA. We expect to find an amount in the ballpark of 3400, give or take a bit for normal variances like read errors or reporting differences.

Shared cM parent child.png

click to enlarge

I did not expect to see a minimum shared cM amount for a child/parent relationship at 2376, fully 1024 cM below expected value of 3400 cM. Put bluntly, that’s simply not possible. You cannot live without one third of one of your parent’s DNA. If this data is actually accurate from someone’s account, please contact me because I want to actually see this phenomenon.

I reached out to Blaine, knowing this result is not actually possible, wondering how this would ever get through the quality control cycle at any vendor.

After some discussion, here’s Blaine’s reply:

If you look at the histogram, you’ll see that those are most likely outliers. One of my lessons for the ScP (Shared cM Project) lately is that people shouldn’t be using the data without the histograms.

People get frustrated with this, but I can’t edit data without a basis even if I think it doesn’t make sense. I have to let the data itself decide what data to remove. So I removed 1% from each relationship, the lowest 0.5% and the highest 0.5%. I could have removed more, but based on the histograms, [removing] more appeared to be removing too much valid data. As people submit more parent/child relationships these outliers/incorrect submissions will be removed. But thankfully using the histograms makes it clear.

Indeed, if you look on page 23 on Blaine’s white paper, you’ll see the following histogram of parent/child relationships submitted.

shared cm histogram.png

click to enlarge

Keep in mind that Blaine already removed any obvious errors, plus 1% of the total from either end of the spectrum. In this case, he utilized 2412 submissions, so he would have removed about 24 entries that were even further out on the data spectrum.

On the chart above, we can see that a total of about 14 are still really questionable. It’s not until we get to 3300 that these entries seem feasible. My speculation is that these people meant to type 3400 instead of 2400, and so forth.

shared cm parent grid.png

click to enlarge

The great news is that Jonny Perl at DNAPainter included the histograms so you can judge for yourself if you are in the weeds on the outlier scale by clicking on the relationship.

shared cm parent submissions.png

click to enlarge

Other relationships, like this niece/nephew relationship fit the expected bell shaped curve very nicely.

shared cm niece.png

Of course, this means that if you match your niece or nephew at 900 cM instead of the range shown above, that person is probably not your full niece or nephew – a revelation that may be difficult because of the implications for you, your parent and sibling. This would suggest that your sibling is a half sibling, not a full sibling.

Entering specific amounts of shared DNA and outputting probabilities of specific relationships is where the power of DNAPainter enters the picture. Let’s enter 900 cM and see what happens.

shared cm half niece.png

That 900 cM match is likely your half niece or nephew. Of course, this example illustrates perfectly why some relationships are entered incorrectly – especially if you don’t know that your niece or nephew is a half niece or nephew – because your sibling is a half-sibling instead of a full sibling. Some people, even after receiving results don’t realize there is a discrepancy, either because their data is on the boundary, with various relationships being possible, or because they don’t understand or internalize the genetic message.

shared cm full siblings.png

click to enlarge

This phenomenon probably explains the low minimum value for full siblings, because many of those full siblings aren’t. Let’s enter 1613 and see what DNAPainter says.

shared cm half sibling.png

You’ll notice that DNAPainter shows the 1613 cM relationship as a half-sibling.

shared cm sibling.png

And the histogram indeed shows that 1613 would be the outlier. Being larger that 1600, it would appear in the 1700 category.

shared cm half vs full.png

click to enlarge

Accurately discerning close relationships is often incredibly important to testers. In the histogram chart above, you can see that the blue and orange histograms plotted on the same chart show that there is only a very small amount of overlap between the two histograms. This suggests that some people, those in the overlap range, who believe they are full siblings are in reality half-siblings, and possibly, a few in the reverse situation as well.

What Else is Noteworthy?

First, some relationships cannot be differentiated or sorted out by using the cM data or histogram charts alone.

shared cm half vs aunt.png

click to enlarge

For example, you cannot tell the difference between half-siblings and an aunt/uncle relationship. In order to make that determination, you would need to either test or compare to additional people or use other clues such as genealogical research or geographic proximity.

Second, the ranges of many relationships are wider than they were before. Often, we see the lows being lower and the highs being higher as a result of more data.

shared cm low high.png

click to enlarge

For example, take a look at grandparents. The expected relationship is 1700 cM, the average is 1754 which is very close to the previous average numbers of 1765 and 1766. However, the minimum is now 984 and the new maximum is 2462.

Why might this be? Are ranges actually wider?

Blaine removed 1% each time, which means that in V3, 6 results would have been removed, 3 from each end, while 11 would be removed in V4. More data means that we are likely to see more outliers as entries increase, with the relationship ranges are increasingly likely to overlap on the minimum and maximum ends.

Third, it’s worth noting that several relationships share an expected amount of DNA that is equal, 12.5% which equals 850 cM, in this example.

shared cm 4 relationships.png

click to enlarge

These four relationships appear to be exactly the same, genetically. The only way to tell which one of these relationships is accurate for a given match pair, aside from age (sometimes) and opportunity, is to look at another known relationship. For example, how closely might the tester be related to a parent, sibling, aunt, uncle or first cousin, or one of their other matches. Occasionally, an X chromosome match will be enlightening as well, given the unique inheritance path of the X chromosome.

Additional known relationships help narrow unknown relationships, as might Y DNA or mitochondrial DNA testing, if appropriate. You can read about who can test for the various kinds of tests, here.

Fourth, it’s been believed for several years that all 5th degree relatives, and above, match, and the V4 data confirms that.

shared cm 5th degree.png

click to enlarge

There are no zeroes in the column for minimum DNA shared, 4th column from right.

5th degree relatives include:

  • 2nd cousins
  • 1st cousins twice removed
  • Half first cousins once removed
  • Half great-aunt/uncle

Fifth, some of your more distant cousins won’t match you, beginning with 6th degree relationships.

shared cm disagree.png

click to enlarge

At the 6th degree level, the following relationships may share no DNA above the vendor matching threshold:

  • First cousins three times removed
  • Half first cousins twice removed
  • Half second cousins
  • Second cousins once removed

You’ll notice that the various reporting models and versions don’t always agree, with earlier versions of the Shared cM Project showing zeroes in the minimum amount of DNA shared.

Sixth, at the 7th degree level, some number of people in every relationship class don’t share DNA, as indicated by the zeros in the Shared cM Minimum column.

shared cm 7th degree.png

click to enlarge

The more generations back in time that you move, the fewer cousins can be expected to match.

shared cm isogg cousin match.png

This chart from the ISOGG Wiki Cousin statistics page shows the probability of matching a cousin at a specific level based on information provided by testing companies.

Quick Reference Chart Summary

In summary, V4 of the Shared cM Project confirms that all 2nd cousins can expect to match, but beyond that in your trees, cousins may or may not match. I suspect, without evidence, that the further back in time that people are related, the less likely that the proper “cousinship level” is reported. For example, it would be easier to confuse 7th and 8th cousins as compared to 1st and 2nd cousins. Some people also confuse 8th cousins with 8 generations back in your tree. It’s not equivalent.

shared cm eighth cousin.png

click to enlarge

It’s interesting to note that Degree 17 relatives, 8th cousins, 9 generations removed from each other (counting your parents as generation 1), still match in some cases. Note that some companies and people count you as generation 1, while others count your parents as generation 1.

The estimates of autosomal matching reaching 5 or 6 generations back in time, meaning descendants of common 4 times great-grandparents will sometimes match, is accurate as far as it goes, although 5-6 generations is certainly not a line in the sand.

It would be more accurate to state that:

  • 2nd cousins, people descended from common great-grandparents, 3 generations back in time will always match
  • 4th cousins, people descended from common 3 times great grandparents, 5 generations back in time, will match about half of the time
  • 8th cousins, people descended from 7 times great grandparents, 9 generations back in time still match a small percentage of the time
  • Cousins from more distant ancestors can possibly match, but it’s unlikely and may result from a more recent unknown ancestor

I created this summary chart, combining information from the ISOGG chart and the Shared cM Project as a handy quick reference. Enjoy!

shared cm quick reference.png

click to enlarge

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Disclosure

I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

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DNA Inherited from Grandparents and Great-Grandparents

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28

Philip Gammon, our statistician friend has been working with crossover simulations again in order to tell us what we might expect relative to how much DNA we actually inherit from grandparents and great-grandparents.

We know that on average, we’re going to inherit 25% of our DNA from each grandparent – but we also know in reality that’s not what happens. We get more or less than exactly 25% from each person in a grandparent pair. It’s the total of the DNA of both grandparents that adds up to 50% for the couple.

How does this work, and does it make a difference whether we inherit our grandparent’s DNA through males or females?

Philip has answers for us as a result of his simulations.

DNA Inheritance from Grandparents

Philip Gammon:

When we consider the DNA that we inherit from our ancestors the only quantity that we can be certain of is that we receive half of our autosomal DNA from each parent. This is delivered to us in the form of the 22 segments (i.e. chromosomes) provided by our mothers in the ova and the 22 segments/chromosomes provided by our fathers in the sperm cell. Beyond parent-child relationships we tend to talk about averages. For instance, we receive an average of one quarter of our DNA from each of our four grandparents and an average of one-eighth of our DNA from each of our eight great-grandparents etc.

These figures vary because our parents didn’t necessarily pass on to us equal portions of the DNA that they received from their parents. The level of variation is driven by the number (and location) of crossover events that occur when the ova and the sperm cells are created.

The statistics relevant to the recombination process were discussed in detail in a previous article (Crossovers: Frequency and Inheritance Statistics – Male Versus Female Matters). With the availability these days of abundant real data from direct-to-consumer genetic testing companies (such as the 23andMe data utilised by Campbell et. al. in their paper titled “Escape from crossover interference increases with maternal age”) we can use this information as a basis for simulations that accurately mimic the crossover process. From these simulations we can measure the amount of variation that is expected to be observed in the proportions of DNA inherited from our ancestors. This is precisely what I have done in simulations run on my GAT-C model.

Before looking at the simulation results let’s anticipate what we expect to see. The previous article on crossover statistics revealed that there are an average of about 42 crossovers in female meiosis and about 27 in male meiosis. So, on the set of 22 chromosomes received from our mothers there will have been an average of 42 crossover locations where there was a switch between DNA she inherited from one parent to the other. That means that the DNA we inherit from our maternal grandparents typically comes in about 64 segments, but it won’t necessarily be 32 segments from each maternal grandparent. Chromosomes that experienced an odd number of crossovers contain an even number of segments (half originating from the grandmother, the other half from the grandfather) but chromosomes with an even number of crossovers (or zero!) have an odd number of segments so on these chromosomes you must receive one more segment from one grandparent than the other. And of course not all segments are the same size either. A single crossover occurring close to one end of the chromosome results in a small segment from one grandparent and a large segment from the other. All up there are quite a few sources of variation that can affect the amount of DNA inherited from grandparents. The only certainty here is that the amount inherited from the two maternal grandparents must add to 50%. If you inherit more than the average of 25% from one maternal grandparent that must be offset by inheriting less than 25% from the other maternal grandparent.

Gammon grandparents maternal percent.png

The above chart shows the results of 100,000 simulation runs. Excluding the bottom and top 1% of results, 98% of people will receive between 18.7% and 31.3% of their DNA from a maternal grandparent. The more darkly shaded region in the centre shows the people who receive a fairly even split of between 24% and 26% from the maternal grandparents. Only 28.8% of people are in this region and the remainder receive a less even contribution.

On the set of 22 chromosomes received from fathers there will have been an average of around 27 crossovers so the DNA received from the paternal grandparents has only been split into around 49 segments. It’s the same amount of DNA as received from mothers but just in larger chunks of the grandparent’s DNA. This creates greater opportunity for the father to pass on unequal amounts of DNA from the two grandparents so it would be expected that results from paternal inheritance will show more variation than from maternal inheritance.

Gammon grandparents paternal percent.png

The above chart shows the results of 100,000 simulated paternal inheritance events. They are more spread out than the maternal events with the middle 98% of people receiving between 16.7% and 33.3% of their DNA from a paternal grandparent. Only 21.9% of people receive a fairly even split of between 24% and 26% from each paternal grandparent as shown by the more darkly shaded region in the centre.

Gammon grandparents percent cM.png

To help with the comparison between maternal and paternal inheritance from grandparents the two distributions have been overlayed on the same scale in the chart above. And what are the chances of receiving a fairly even split of grandparents DNA from both your mother and your father? Only 6.3% of people can be expected to inherit an amount of between 24% and 26% of their DNA from all four grandparents.

Now I’ll extend the simulations out to the next generation and examine the variation in proportions of DNA inherited from the eight great-grandparents. There are effectively four groups of great-grandparents:

  • Mother’s maternal grandparents
  • Mother’s paternal grandparents
  • Father’s maternal grandparents
  • Father’s paternal grandparents

The DNA from group 1 has passed to you via two maternal recombination events, from your mother’s mother to your mother, then from your mother to you. On average there would have been 42 crossovers in each of these recombination events. Group 4 comprised two paternal recombination events averaging only 27 crossovers in each. The average amount of DNA received along each path is the same but along the group 1 path it would comprise of more numerous smaller segments than the group 4 path. Groups 2 and 3 would be somewhere between, both consisting of one maternal and one paternal recombination event.

Gammon greatgrandparents percent cM.png

The above chart shows the variation in the amount of DNA received from members of the four groups of great-grandparents. 25,000 simulations were performed. The average amount from any great-grandparent is 12.5% but there can be considerably more variation in the amount received from the father’s paternal grandparents than from the mother’s maternal grandparents. Groups 2 and 3 are between these two extremes and are equivalent. It doesn’t matter whether a paternal recombination follows a maternal one or vice versa – the end result is that both paths consist of the same average number of crossovers.

The table below shows the range in the amount of DNA that people receive from their great-grandparents. The bottom and top 1% of outcomes have been excluded. Note that these are based on a total of 3,418 cM for the 22 autosomes which is the length observed in the Campbell et. al. study. The average of 12.5% of total DNA is 854.5 cM:

Group 1st percentile 99th percentile
Mother’s maternal grandparents 522 cM 1219 cM
Mother’s paternal grandparents 475 cM 1282 cM
Father’s maternal grandparents 475 cM 1281 cM
Father’s paternal grandparents 426 cM 1349 cM

As a matter of interest, in each of the 25,000 simulations the amount of DNA received from the eight great-grandparents were sorted into order from the highest cM to the lowest cM. The averages of each of these eight amounts were then calculated and the results are below:

Gammon greatgrandparents average cM.png

On average, a person receives 1,129 cM from the great-grandparent that they inherited the most of their DNA from and only 600 cM from the great-grandparent that they received the least of their DNA from. But none of us are the result of 25,000 trials – we are each the product of recombination events that occurred once only. The above chart shows the average or typical variation in the amount of DNA received from the eight great-grandparents. Half of people will have experienced more variation than shown above and half of people will have experienced less variation.

Could you have received the same amount of DNA from all eight grandparents? Of course, it is possible, but it turns out that it is extremely unlikely. The average is 12.5% (854.5 cM) so anything between 12% (820.4 cM) and 13% (888.7 cM) could be considered as being close to this figure. The results reveal that this did not occur in any of the 25,000 simulations. Not one person received amounts between 12% and 13% from all eight great-grandparents.

Widening the criteria, I observe that there were 13 instances in the 25,000 simulations where people received between 11.5% and 13.5% of their DNA from all eight great-grandparents. That is still an extremely rare occurrence. Expanding the range further to between 11% and 14% saw a total of 126 instances, but this still only represents about half a percent of all observations. I think that we just have to face the fact that unless we are an extremely rare individual then we will not have inherited close to equal amounts of DNA from our eight great-grandparents.

Now, back to Roberta.

Thanks Philip.

Now we see why we might not inherit the same amount of DNA from our grandparents and great-grandparents.

We Don’t Have Equal Numbers of Matches on Tree Branches

This also might explain, at least in part, why people don’t have the same number of DNA matches on each branch of their tree.

Of course, other reasons include:

  • Uneven family sizes
  • Fewer or more cousins testing on different branches
  • Recent immigration meaning there are few people available to test
  • Family from a region where DNA testing and/or genealogy is not popular
  • Endogamy which dramatically increases the number of people you will match

Real Life Example

In our real-life example, two grandchildren are fortunate to have three grandparents and one great-grandparent available for matching.

For comparison purposes, let’s take a look at how many matches each grandchild has in common with their grandparents and great-grandparent.

The line of descent is as follows:

Gammon line of descent.png

Both end of line testers are female children.

The transmission path from their great-grandmother is:

  • Female to their paternal grandmother
  • Female to their father
  • Male to female tester

The transmission path from their maternal grandfather is:

  • Male to their mother
  • Female to female tester

The transmission path from their maternal grandmother is:

  • Female to their mother
  • Female to female tester

This first chart shows the number of common matches.

Matches Grand 1 Grand 2 GGF GGM Grand 3 Grand 4
Female 1 absent 1061 absent 238 529 1306
Female 2 absent 1225 absent 431 700 1064

It’s interesting that the matches in just 3 generations to the great-grandmother vary by 55%. The second tester has almost twice as many matches in common with her great-great-grandmother as she does the first tester. There a difference in the earlier generation, meaning matches to Grand 2, but only about 23%. That difference increased significantly in one generation.

The second chart shows the total number of matching cM with the matching family member.

Total cM Grand 1 Grand 2 GGF GGM Grand 3 Grand 4
Female 1 absent 1688 absent 713 1601 1818
Female 2 absent 1750 absent 852 1901 1511

We can see that the amount of DNA inherited from a grandparent does correlate with the number of matches to that grandparents. The more DNA shared, of course the better the chances of sharing that DNA with another person. However, multiple factors may be involved with why some people have more or fewer matches.

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Disclosure

I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

Genealogy Products and Services

Genealogy Research

Fun DNA Stuff

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Are You DNA Testing the Right People?

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We often want to purchase DNA kits for relatives, especially during the holidays when there are so many sales. (There are links for free shipping on tests in addition to sale prices at the end of this article. If you already know who to test, pop on down to the Sales section, now.)

Everyone is on a budget, so who should we test to obtain results that are relevant to our genealogy?

We tell people to test as many family members as possible – but what does that really mean?

Testing everyone may not be financially viable, nor necessary for genealogy, so let’s take a look at how to decide where to spend YOUR testing dollars to derive the most benefit.

It’s All Relative😊

When your ancestors had children, those children inherited different pieces of your ancestors’ DNA.

Therefore, it’s in your best interest to test all of the direct descendants generationally closest to the ancestor that you can find.

It’s especially useful to test descendants of your own close ancestors – great-great-grandparents or closer – where there is a significant possibility that you will match your cousins.

All second cousins match, and roughly 90% (or more) of third cousins match.

Percent of cousins match.png

This nifty chart compiled by ISOGG shows the probability statistics produced by the major testing companies regarding cousin matching relationships.

My policy is to test 4th cousins or closer. The more, the merrier.

Identifying Cousins

  • First cousins share grandparents.
  • Second cousins share great-grandparents.
  • Third cousins share great-great-grandparents.

The easiest way for me to see who these cousins might be is to open my genealogy software on my computer, select my great-great-grandparent, and click on descendants. Pretty much all software has a similar function.

The resulting list shows all of the descendants of that ancestor that I’ve entered in my software. Most genealogists already have or could construct this information with relative ease. These are the cousins you need to be talking to anyway, because they will have photos and stories that you don’t. If you don’t know them, there’s never been a better time to reach out and introduce yourself.

Who to test descendants software

Click to enlarge

People You Already Know

Sometimes it’s easier to start with the family you already know and may see from time to time. Those are the people who will likely be the most beneficial to your genealogy.

Who to test 1C.png

Checking my tree at FamilyTreeDNA, Hiram Ferverda and Evaline MIller are my great-grandparents. All of their children are deceased, but I have a relationship with the children born to their son, Roscoe. Both Cheryl and her brother carry parts of Hiram and Eva’s DNA their son John Ferverda (my grandfather) didn’t inherit, and therefore that I can’t carry.

Therefore, it’s in my best interest to gift my cousin, Cheryl and her brother, both, with DNA kits. Turns out that I already have and my common matches with both Cheryl and her brother are invaluable because I know that people who match me plus either one of them descend from the Ferverda or Miller lines. This relationship and linking them on my tree, shown above, allows Family Tree DNA to perform phased Family Matching which is their form of triangulation.

It’s important to test both siblings, because some people will match me plus one but not the other sibling.

Who’s Relevant?

Trying to convey the concept of who to test and not to test, and why, is sometimes confusing.

Many family members may want to test, but you may only be willing to pay for those tests that can help your own genealogy. We need to know who can best benefit our genealogy in order to make informed decisions.

Let’s look at example scenarios – two focused on grandparents and two on parents.

In our example family, a now-deceased grandmother and grandfather have 3 children and multiple grandchildren. Let’s look at when we test which people, and why.

Example 1: Grandparents – 2 children deceased, 1 living

In our first example, Jane and Barbara, my mother, are deceased, but their sibling Harold is living. Jane has a living daughter and my mother had 3 children, 2 of which are living. Who should we test to discover the most about my maternal grandparents?

Please note that before making this type of a decision, it’s important to state the goal, because the answer will be different depending on your goal at hand. If I wanted to learn about my father’s family, for example, instead of my maternal grandparents, this would be an entirely different question, answer, and tree.

Descendant test

Click to enlarge

The people who are “married in” but irrelevant to the analysis are greyed out. In this case, all of the spouses of Jane, Barbara and Harold are irrelevant to the grandmother and grandfather shown. We are not seeking information about those spouses or their families.

The people I’ve designated with the red stars should be tested. This is the “oldest” generation available. Harold can be tested, so his son, my first cousin, does not need to test because the only part of the grandparent’s DNA that Harold’s son can inherit is a portion of what his father, Harold, carries and gave to him.

Unfortunately, Jane is deceased but her daughter, Liz, is available to test, so Liz’s son does not need to.

I need to test, as does my living brother and the children of my deceased brother in order to recover as much as possible of my mother’s DNA. They will all carry pieces of her DNA that I don’t.

The children of anyone who has a red star do NOT need to test for our stated genealogical purpose because they only carry a portion of thier parent’s DNA, and that parent is already testing.

Those children may want to test for their own genealogy given that they also have a parent who is not relevant to the grandfather and grandmother shown. In my case, I’m perfectly happy to facilitate those tests, but not willing to pay for the children’s tests if the relevant parent is living. I’m only willing to pay for tests that are relevant to my genealogical goals – in this case, my grandparents’ heritage.

In this scenario, I’m providing 5 tests.

Of course, you may have other family factors in play that influence your decision about how many tests to purchase for whom. Family dynamics might include things like hurt feelings and living people who are unwilling or unable to test. I’ve been known to purchase kits for non-biologically related family members so that people could learn how DNA works.

Example 2: Grandparents – 2 children living, one deceased

For our second example, let’s change this scenario slightly.

Descendant test 2

Click to enlarge

From the perspective of only my grandparents’ genealogy, if my mother is alive, there’s no reason to test her children.

Barbara and Harold can test. Since Jane is deceased, and she had only one child, Liz is the closest generationally and can test to represent Jane’s line. Liz’s son does not need to test since his mother, the closest relative generationally to the grandparents is available to test.

In this scenario, I’m providing 3 tests.

Example 3: My Immediate Family – both parents living

In this third example, I’m looking from strictly MY perspective viewing my maternal grandparents (as shown above) AND my immediate family meaning the genealogical lines of both of my parents. In other words, I’ve combined two goals. This makes sense, especially if I’m going to be seeing a group of people at a family gathering. We can have a swab party!

Descendants - parents alive

Click to enlarge

In the situation where my parents are both living, I’m going to test them in addition to Harold and Liz.

I’m testing myself because I want to work using my own DNA, but that’s not really necessary. My parents will both have twice as many matches to other people as I do – because I only inherited half of each parent’s DNA.

In this scenario, I’m providing 5 tests.

Example 4: My Immediate Family – one parent living, one deceased

Descendants - father deceased

Click to enlarge

In our last example, my mother is living but my father is deceased. In addition to Harold and Liz who reflect the DNA of my maternal grandparents, I will test myself, my mother my living brother and my deceased brother’s child.

Because my father is deceased, testing as many of my father’s descendants as possible, in addition to myself, is the only way for me to obtain some portion of his DNA. My siblings will have pieces of my parent’s DNA that I don’t.

I’m not showing my father’s tree in this view, but looking at his tree and who is available to test to provide information about his side of the family would be the next logical step. He may have siblings and cousins that are every bit as valuable as the people on my mother’s side.

Applying this methodology to your own family, who is available to test?

Multiple Databases

Now that you know WHO to test, the next step is to make sure your close family members test at each of the major providers where your DNA is as well.

I test everyone at Family Tree DNA because I have been testing family members there for 19 years and many of the original testers are deceased now. The only way new people can compare to those people is to be in the FamilyTreeDNA data base.

Then, with permission of course, I transfer all kits, for free, to MyHeritage. Matching is free, but if you don’t have a subscription, there’s an unlock fee of $29 to access advanced tools. I have a full subscription, so all tools are entirely free for the kits I transfer and manage in my account.

Transferring to Family Tree DNA and matching there is free too. There’s an unlock fee of $19 for advanced tools, but that’s a good deal because it’s substantially less than a new test.

Neither 23andMe nor Ancestry accept transfers, so you have to test at each of those companies.

The great news is that both Ancestry and 23andMe tests can be transferred to  MyHeritage and FamilyTreeDNA.

Before purchasing tests, check first by asking your relatives or testing there yourself to be sure they aren’t already in those databases. If they took a “spit in a vial” test, they are either at 23andMe or Ancestry. If they took a swab test, it’s MyHeritage or FamilyTreeDNA.

I wrote about creating a testing and transfer strategy in the article, DNA Testing and Transfers – What’s Your Strategy? That article includes a handy dandy chart about who accepts which versions of whose files.

Sales

Of course, everything is on sale since it’s the holidays.

Who are you planning to test?

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Disclosure

I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

Genealogy Products and Services

Genealogy Research

Fun DNA Stuff

  • Celebrate DNA – customized DNA themed t-shirts, bags and other items